Liquid fuel pumping apparatus



Jan. 16, 1968 F. M. EVANS 3,363,568

LIQUID FUEL PUMPING APPARATUS Filed Dec. 7, 1965 United States Patent Oiiice 3,363,568 Patented Jan. 16, 196B 3,363,568 LIQUID FUEL PUMPING APPARATUS Fraser Mackie Evans, Ickenham, Uxbridge, England, as-

signor to C.A.V. Limited, London, England Filed Dec. 7, 1965, Ser. No. 512,174 3 Claims. (Cl. 103-2) ABSTRACT OF THE DISCLOSURE A fuel pumping apparatus for supplying fuel to internal combustion engines in which fuel is supplied to an injection pump and the setting of a metering valve determines the quantity of fuel delivered to the injection pumpt One face of the metering valve is subjected to the pressure of the fuel delivered and resilient means acts on the valve in opposition to the force produced by the pressure of the fuel on one such face. In addition, means are provided for regulating the pressure on the face of the valve remote from such one face.

This invention relates to liquid fuel pumping apparatus for supplying fuel to internal combustion engines and of the kind comprising an injection pump arranged to be driven in timed relationship to an engine with which the apparatus is associated for supplying fuel to a combustion space of the engine, means for supplying fuel to the injection pump at a pressure dependent upon the speed of the engine, a metering valve the setting of which determines the quantity of fuel supplied by the feed pump to the injection pump, one face of said metering valve being exposed to the output pressure of the feed pump, first resilient means acting on said metering valve in oppo sition to the force produced by the pressure of fuel acting on said face, and control means whereby the setting of the metering valve at any given delivery pressure of the feed pump can be varied.

The object of this invention is to provide an apparatus of the kind specified in a simple and convenient form.

The sole figure of the accompanying drawing is a View partly in elevation and partly in cross-section of one example of a liquid fuel pumping apparatus in accordance with the invention and in which there is provided a body part in which is mounted a rotary distributor 11 which is arranged to be driven in timed relationship to an engine with which the apparatus is associated. At one end of the distributor there is formed a transverse bore 12 in which is slidably mounted a pair of plungers 13, these being arranged, to be moved inwardly, as the distributor rotates through rollers 14, by the action of a plurality of inwardly directed cam lobes formed on the internal periphery of a ring 15 surrounding the distributor. Formed in the distributor is a longitudinal bore 16 which at one end communicates with the aforesaid transverse bore and which at its other end terminates in a radial delivery passage 17 which communicates in turn and as the distributor rotates, with a plurality of equi-angularly spaced delivery ports 18 formed in the body part and which communicate respectively with injection nozzles (not shown) mounted so as to direct fuel into the combustion spaces of the engine respectively.

At another point the longitudinal bore 16 communicates with a plurality of radially disposed and equiangularly spaced inlet passages 19 which communicate in turn with an inlet port 20 defined in the body part and which communicates with a source of fuel under pressure. The pump so far described operates in a well known manner this being that when one of the inlet passages 19 is in register with the inlet'port 20 fuel flows from the latter to the transverse bore 12 and causes the plungers 13 therein to be moved outwardly. As the distributor rotates the inlet passage is moved out of register with the inlet port and the delivery passage 17 is moved into communication with an outlet port 18 and whilst the latter communication is established the plungers 16- are moved inwardly by the cam lobes and fuel is displaced from the transverse bore 12 and flows through the longitudinal bore 16 and delivery passage to one of the aforesaid injection nozzles and to a combustion space of the engine. As the distributor further rotates the inward movement of the plungers stops and the communication between the delivery passage and outlet ports is broken and the communication between the inlet port and one of the inlet passages is reestablished whcreafter the cycle is repeated and fuel is delivered to the combustion spaces of the engine in turn.

Fuel is delivered to the inlet port 20 by a feed pump 21 which is mounted within the body part 10 and which has a vaned rotor 22 arranged to be driven by the distributor. The feed pump has an inlet 23 and an outlet 24 in the body and the inlet is connected in use, to an external source of fuel. Moreover, the outlet pressure of the feed pump is controlled by a control valve 25 of the spring loaded type although this may be replaced by a centrifugally operable valve. In either case the output pressure of the feed pump varies in a manner dependent upon the speed at which the associated engine is running.

The amount of fuel which can pass to the bore whilst communication between the inlet port 20 and one of the inlet passages 19 is established is controlled so that the quantity of fuel which is delivered to the engine at each injection stroke, is controlled. For this purpose there is provided a stepped cylinder 26 in the body part and in the narrower part of this cylinder is mounted an axially movable metering valve in the form of a close fitting cylindrical member 27. The narrower end of the cylinder is in communci-ation with the outlet 24 of the feed pump by way of a circumferential groove in the distributor and in the wider portion of the cylinder is mounted an axially movable cylindrical plug 28. Moreover, mounted intermediate the plug 28 and the member 27 is a first coiled compression spring 29 and mounted intermediate the plug 2 8 and the wider end of the cylinder is a second coiled compression spring 30. The rates of the two springs are unequal and in fact, the rate of the spring 30 is lower than that of the spring 29.

Intermediate the ends of the member 27 there is provided an annular groove 27a which is in communication with the narrow end of the cylinder 26 by way of an axial passage 27b within the member 27. Moreover, in the wall of the cylinder 26 is a port 31 which is in communication with the inlet port 20 and with the aforesaid groove in the member 27. The effective size of the port 3'1 is controlled by an edge of the groove 27a and the arrangement is such that the further the member 27 is moved against the action of the springs the smaller is the effective size of the port 31 thereby reducing the quantity of fuel fed to the engine.

The wider end of the cylinder is in communication with the inlet 23 and the feed pump 21 via a conduit 26a and a space 26b intermediate the member 27 and the plug 28 is supplied with fuel from the outlet 24 of the feed pump through a restricted orifice 3-2 formed in the axial passage 27b in the member 27. The pressure of the fuel in the aforesaid space is controlled by a spring loaded relief valve 33 in communication therewith by conduit 33a, the blow off pressure of which can be adjusted by an operator adjustable lever 34. Moreover, a stop 35 is provided in the wider end of the cylinder 26 to limit the amount of movement of the plug 28 against the action of the spring 30. A conduit 33b leads from the relief valve 33 to the conduit 26a.

The arrangement is such that in use, when the engine is required to idle the relief valve 33 is set to blow oil at a low pressure with the result that the pressure in the aforesaid space 2612 and consequently the pressure acting on the end of the member 27 adjacent the spring 29 is at a minimum. Moreover, the force produced by the spring 30 is sufficient to move the plug 18 away from the stop 35. Consequently the force produced by the output pressure of the feed pump acting on the member 27 is balanced by the spring 30 and since this is a low rate spring the member is able to respond quickly to change in the outlet pressure of the engine so that the idling speed of the engine is closely controlled. It should be noted that an increase in the speed of the engine results in a higher pressure at the outlet 24 of the feed pump 21 with the result that the member 27 moves to reduce the effective size of the port 31 and the quantity of fuel supplied to the engine is reduced.

When the operator desires to increase the speed of the engine the lever 34 is adjusted to increase the pressure at which the relief valve 33 opens and when this is done the pressure in the space 26b rises to the output pressure of the feed pump, owing to the fact that no flow of fuel occurs through the restriction 32, with the result that the member 27 is moved by the spring 29 in a direction to increase the quantity of fuel supplied to the engine, and also the plug 28 is moved further towards, or if the outputgiressure is high enough, against the stop 35. As the speed of the engine increases a point is reached at which the relief valve 33 opens and the fuel flow occurs through the orifice 32 and the pressure in the space 26!) falls so that the member 27 is moved against the action of the spring 29, to reduce the quantity of fuel supplied to the engine, until an equilibrium is established. When the plug 28 is in eotnact with the stop only the spring 29 acts on the member 27, and since this is a high rate spring the sensitivity of the member to changes in the output pressure of the feed pump and consequently to the speed of the engine is lower than when the spring 29 is in action. It will be appreciated that the spring 29 is not suddenly rendered inactive as the speed of the engine varies but that it is a gradual process with the result that the sensitivity of the valve member to changes in the output pressure of the feed pump gradually decreases with the increasing speed. It will further be appreciated that the combination of a spring loaded member and a relief valve as has been described act as an hydraulic governor to control the speed of the engine for a. given setting of the lever.

It will be appreciated that the control valve 33 and the associated lever 34 are mounted at a remote point from the pumping apparatus thereby making the arrangement particularly useful for use on vehicles in which the engine is mounted at a remote point from the driver. Furthermore, if the feature of variation in sensitivity is not required the plug 28 may be fixed and merely serve as an abutment for the spring 29. In this case the spring 30 and abutment 35 would be omitted.

This invention is not to be eonfined to any strict eonformity to the showings in the drawings but changes or modifications may be made therein so long as such changes or modifications mark no material departure from the spirit and scope of the appended claims,

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A liquid fuel pumping apparatus for supplying fuel to the combustion spaces of an internal combustion engine, comprising a body, a rotary distributor within the body adapted to be driven in timed relationship to the engine, said body having a plurality of equi-angularly spaced delivery ports by means of which fuel is directed into the combustion spaces and an inlet port, said distributor having a longitudinal bore therein, pumping means in communication with the bore, a radial delivery passage leading from the longitudinal bore for communication with the delivery ports, a plurality of radially disposed and equi-angularly spaced inlet passages in the distributor for communication with the bore and the inlet port, complemental means in the body and distributor for delivering fuel to the inlet port and a metering valve assembly in the body for determining the quantity of fuel delivered by said complemental means to the pumping means via the inlet port, inlet passages and bore, said metering valve assembly including a first cylinder for the body in communication with said complemental means, an axially movable member disposed in said cylinder, said movable member having an axial passage and an annular groove therein with said groove being in communication with the cylinder via said axial passage, port means in the body for providing communication between said annular groove and inlet port, a second cylinder for the body of larger diameter than the first cylinder and in axial alignment with the first cylinder, means providing communication between the second cylinder and the complemental means for delivering fuel to the inlet port, an axially movable plug in the second cylinder, spring means biased between the plug and the axially movable member, further spring means of lower rate than the first spring means biased between the plug and the closed end of the second cylinder, an adjustable spring-loaded relief valve and means providing communication between the springloaded relief valve and the space of the second cylinder intermediate the axially movable plug and the axially movable member, whereby at idling speed and the relief valve set to blow-off at low pressure, the pressure in the intermediate space acting on the end of the movable member is at a minimum and the force produced by the output pressure of the complemental means is balanced by the further spring means.

2. The liquid fuel pumping apparatus as claimed in claim 1 including stop means in said second cylinder for limiting the amount of movement of said plug against the action of said further spring means.

3. The liquid fuel pumping apparatus as claimed in claim 2 in which said movable member is provided with a restricted orifice leading to said axial passage and through which fuel enters the intermediate space.

References Cited UNITED STATES PATENTS 2,384,340 9/1945 Reggie 123-1 40 2,942,619 6/1960 Jackson 103-40 3,161,133 12/1964 Hutcheon 1032 3,288,124 11/1966 Roosa 123-440 LAURENCE M. GOODRIDGE, Primary Examiner. 

